With the rapid development of integrated circuit technology, the characteristic dimension of integrated circuits decreases rapidly, which brings many advantages, such as increasing level of integration of integrated circuits, reducing circuit delay and reducing the cost of integrated circuits, etc., but it also brings some problems. A relatively common problem is: When the characteristic dimension of integrated circuits decreases, the threshold voltage of the transistor in it decreases, thus, when the voltage difference between the gate electrode and the source electrode of the transistor is 0 and the transistor is in the shut-off state, the shutoff-state current of the transistor increases.
Low-power integrated circuit is a rapid developing area in integrated circuit field in recent years, particularly in practical applications such as industrial control and medical field, low-power integrated circuits has broad prospects for development. Low-power integrated circuits requires the shutoff-state current of transistors is very small, so as not to affect its standby time which can be several months or even several years. And after the characteristic dimension of integrated circuit decreases, the increase of shutoff-state current of the transistor and requirements of low-power integrated circuit were in conflict with each other.
In general, by increasing the channel length of the transistor L, the shutoff-state current of the transistor can be reduced. A conventional transistor shutoff-state circuit is shown in FIG. 1, when the switch S1 is turned on, the gate electrode and the source electrode of the N-type metal-oxide-semiconductor (NMOS) transistor N1 short-circuited, the voltage difference between the gate electrode and the source electrode of the NMOS transistor N1 is 0, at this moment, the NMOS transistor N1 is in the shut-off state; by increasing the channel length L of the NMOS transistor N1, the drift length of charge carriers in the channel area can be increased, thereby reduces the shutoff-state current of NMOS transistor N1. However, increasing the channel length L of the NMOS transistor N1 is bound to cause the increase in transistor size, which further causes increase in the overall size of the integrated circuit and increase of the cost of the integrated circuit chip.